1. Field of the Invention
This invention relates generally to the transfer or transport of medical patients from one place to another within medical facilities as well as other locations and, more particularly, to air pallet or mat-type patient transfer apparatus for facilitating safe and comfortable support and transfer of medical patients from beds to gurneys or stretchers, or the reverse, particularly when the patient is to be transported or moved from one department or location in a hospital to another department or location in the same institution for various medical, surgical or diagnostic procedures. More particularly still, the invention relates to the use and structure of a semirigid air pallet in which one or more compressed air-filled chambers form a mat having a plurality of orifices in the bottom from which compressed air is released to support the mat slightly above the surface of beds, gurneys or the like or other surfaces allowing it to be moved in any direction desired over such surfaces.
2. Prior Art
Medical patients, including accident victims, the very elderly, comatose patients, patients paralyzed by strokes and other medical problems and the like, are frequently difficult to transfer or move in a safe, comfortable manner from one support surface such as a bed or the like to another support surface such as a gurney, or wheeled hospital cart, or the like, or from a stretcher or the like to a gurney, and finally, to a bed in a hospital or other medical facility. Patients who cannot sit up or move themselves are frequently particularly difficult to move from a stretcher to a bed or vice versa, frequently requiring two or three husky nurses or attendants with an ever present possibility of causing back injury and lost time to the medical personnel themselves, particularly if the patient is unusually heavy, as a disproportionate number of particularly troublesome or difficult to handle patients tend to be. In recent years, various transferrers or patient transfer or moving apparatus have been developed which can be placed either temporarily or semipermanently under a patient already on a bed or on a stretcher or the like and then inflated and moved onto another surface together with the patient. These transfer devices frequently take the form of air mattress-type movers. Such air mattress-type movers or transferrers have been provided with small perforations in the bottom plus a portable supply of compressed air to obtain and at least temporarily maintain inflation. During such inflation, a continuous supply of pressurized air is expelled from the bottom of the transfer device supporting the inflated transfer device or mat on any reasonably flat semi-continuous surface with a patient on top in the general manner of an air pallet sometimes used for industrial transportation within shops and plants.
Earlier examples of this general type of apparatus are, for example, disclosed in U.S. Pat. No. 3,948,344 entitled "LOW COST PLANAR AIR PALLET MATERIAL HANDLING SYSTEM", issued Apr. 6, 1976, and U.S. Pat. No. 4,272,856 entitled "DISPOSABLE AIR-BEARING PATIENT MOVER AND VALVE EMPLOYED THEREIN", issued Jun. 16, 1981, both of which used a low cubic foot per minute air flow which exited from a lower plenum chamber through a thin, flexible bottom sheet perforated by small, closely spaced pinholes over a surface area defined generally by the imprint or outline of the load, which pinholes during use would face an underlying, generally planar, support surface. The pinholes opened to the interior of the plenum chamber and ejected low pressure air directly upon a more or less planar support surface. Consequently, when the plenum chamber was filled or pressurized by low pressure air, such air would be initially blocked from passing through the orifices by the barrier presented by the planar surface upon which the air pallet rested. However as such air pressure increased, such pressure would lift or jack the load upwardly above the thin, perforated, flexible sheet as the pallet or patient mover inflated. Then, when the pallet or mover was completely inflated, the pressure therein would increase until the air began to escape under pressure through the minute pinholes, thereby creating a thin, frictionless air bearing between the underlying support surface and the bottom of the perforated flexible sheet upon which air bearing the air pallet plus any load or patient resting thereupon could be slid in any direction in which the air pallet was urged by a lateral force.
In all air pallets, including transfer devices for medical patients, it is necessary to provide a controlled pillowing or flexibility of the thin, flexible sheet material of the pallet, particularly beyond the perforated surface area of the sheet in order to initially jack the load above the flexible perforated bottom sheet prior to the creation of the frictionless air bearing by excess internal pressure as well as to insure the ability of the air pallet to ride over surface projections on the underlying support surface which may cause upward localized movement of the thin perforated bottom sheet. However, some means must also be provided within the air pallet to prevent ballooning of the unperforated top sheet as well as the thin, flexible perforated bottom sheet defining the plenum chamber. Otherwise, the plenum chamber would tend to expand vertically toward the ultimate assumption of a circular or near circular vertical cross section, the result of which vertical expansion would be loss of contact of substantial portions of the bottom sheet with the underlying surface and tilting or rolling of the load off the top of the air pallet. In addition, when the load rests on the air pallet prior to the pressurization of the plenum chamber, the load tends to press the perforated flexible sheet into contact with the underlying support surface and the upper sheet into contact with the bottom sheet which prevents the entry of air under light pressure into the plenum chamber. Consequently, it has been found that some form of dispersion means are usually required either interiorly or exteriorly of the plenum chamber to ensure proper pressurization of the plenum chamber.
Under certain circumstances, the load itself may constitute a generally rigid or semirigid backing member. For example, in the case of a cardboard box filled with material for transport, the bottom of the box may have the planar bottom function as a generally rigid backing member preventing either the upper or lower flexible sheet from ballooning so long as the internal pressure does not become too high. Even a fairly large bag of grain superimposed as the load may serve as an effective generally rigid backing member to prevent ballooning of an underlying support pallet. In the case of a human body, such as that of a medical patient, resting on the thin upper surface of a patient mover, however, the load is neither flat nor rigid and the top of the pallet will merely tend to inflate on one side or the other of the patient's body and progressively roll such patient off the side of the pallet. Meanwhile, inflation or ballooning of the bottom of the pallet will likewise cause the bottom of the entire pallet to tend to assume an arcuate configuration and as a result rock to the side aiding in rolling the patient off onto the floor or other underlying surface.
In the early development of air bearing patient movers as exemplified by U.S. Pat. No. 3,948,344, a corrugated sheet placed within the single chamber of the mat functioning as a plenum chamber prevented ballooning of the two superimposed thin, flexible sheets by opposing decrease of lateral dimensions. In U.S. Pat. No. 4,272,856 a more or less rigid member constitutes both a unitary air dispersion medium and a semirigid backing member. The semirigid backing member might comprise a semirigid sheet inserted within a cavity formed between the top thin, flexible sheet and an intermediate thin, flexible sheet. Alternatively, the backing member might, in certain later constructions, be formed of a series of transversely-linked, air-pressurized tubes formed by sealing off parallel, laterally-adjacent, longitudinal sections of the top sheet and an intermediate sheet. Such tubes might be completely sealed and air pressurized through valves. In a flow-through system, on the other hand, the pressurized air forming the air bearing passes first through the parallel, transversely-linked tubes defined by the top and intermediate sheets, and then into a separate lower plenum chamber defined by the intermediate sheet and the bottom sheet with the bottom sheet having a series of perforations, the pattern of perforations usually being confined to the outline or footprint of the load. U.S. Pat. No. 4,528,704 issued to Jack Wegener and Raynor D. Johnson, on Jul. 16, 1985 and entitled "SEMI-RIGID, AIR PALLET-TYPE PATIENT MOVER" is directed to air pallets of this general nature.
U.S. Pat. No. 4,417,639 issued to Jack Wegener on Nov. 29, 1983, and entitled "DYNAMIC GAS PRESSURIZED JACKING STRUCTURE WITH IMPROVED LOAD STABILITY AND AIR PALLET EMPLOYING SAME," on the other hand, discloses a flow-through chamber connected by succeedingly smaller sized ports within a series of horizontally extending vertically spaced walls forming a series of stacked chambers in the form of a gas-pressurized jacking structure and an air pallet including such jacking structure. FIG. 10 of such patent shows a jacking structure formed totally of thin, flexible sheet material with vertically separated chambers in communication via a gas passage whose cross-sectional area is smaller than that of the air inlet to the upper chamber.
U.S. Pat. No. 4,686,719 entitled "SEMI-RIGID AIR PALLET-TYPE PATIENT MOVER", discloses a semirigid, air pallet-type patient mover having U-straps sewn to the lateral sides of the mover structure for facilitating lateral shifting of the patient placed thereon while the plenum chamber is pressurized and a thin-air film underlying the perforated area of the thin, flexible bottom sheet provides an air bearing. The patient may be bound to the top of the patient mover via a pair of crossed VELCRO hook-and-loop material-covered straps for ease in engagement and disengagement of the strap ends about the patient.
Air pallets and particularly patient mover type-pallets, which are usually formed of multiple, thermal bonded or stitched sheets of thin, flexible sheet material have in the past, as explained above, frequently incorporated a rigid or a semirigid sheet as the load-backing member. However, such a construction has not been universally employed in health care treatment facilities. The existence of the rigid or semirigid sheet carried within a pocket or cavity defined by two thin, flexible sheets renders the assembly bulky, and adds considerably to the weight. The lack of flexibility may also prevent passage of the transfer devices or patient movers through narrow passages. While such patient movers may perform extremely well at discrete hospital treatment stations or treatment areas such as, for example, where the patient mover may be used for facilitating patient movement onto and from an X-ray table, the patient mover tends to remain at its primary area and is unlikely to be employed in moving the patient to and from hospital beds remote from the X-ray area, since hospital personnel tend to resist transporting such a patient mover from location to location.
The same is true where air pallets in the form of patient movers are utilized by paramedics, shock trauma units or the like. As a result, there has more recently been considerable interest in the development of soft pad or hard pad air chamber-type air pallets as patient movers or as patient positioners. In the health care field, the person moved or whose position is being changed may not in many cases be truly a patient recovering from sickness, but a person requiring continuous attention, such as an invalid or partial invalid. In this case, upon either transport, or positioning and maintaining the patient comfortable in a given partially upright or supine position, there is a distinct possibility of a tissue breakdown if the patient remains in such given positions for significant periods of time. In general, a flexible patient mover causes less tissue breakdown of this nature than a rigid patient mover.
Successful operation of a rigid backing surface-type air pallet requires (a) controlled jacking, (b) controlled pillowing and (c) anti-ballooning. Control of load distribution may be achieved by the use of a rigid backing member such as a board or sheet as part of the plenum chamber, or within a separate chamber supporting the load, but overlying the plenum chamber. The rigid backing member distributes the load mass balanced equally over the area of the plenum chamber footprint. The control of the plenum chamber can also be performed in several other ways and a properly designed plenum chamber can effect several of the control functions, i.e., regulation of jacking, pillowing and ballooning.
Where, for example, the thin, flexible bottom sheet is tightly connected at opposite sides to a generally rigid backing member, such rigid backing member itself will function to control jacking, pillowing and ballooning. Where the rigid backing member is smaller than the thin, flexible bottom sheet, however, slack develops within the thin, flexible bottom sheet and such slack increases the pillowing capability of the thin, flexible bottom sheet. Excessive slack leads ultimately, however, to ballooning.
Other means have in the past been provided for controlling pillowing, such as the lamination of additional members to a center sheet or to either the upper thin, flexible sheet or the bottom thin, flexible sheet. The addition of internal strips lying diagonally from corner to corner within the plenum chamber or vertical from face to face have also been used to control the degree of pillowing. The load itself, as explained above, may act as a pillowing control means. The insertion of a rigid plate internally within a thin, flexible bag may act both as a rigid backing member, a pillowing control means and, under certain conditions, an air distribution means for insuring air pressurization of the plenum chamber with the air pallet formed principally by the bag supporting the load prior to air pressurization of that plenum chamber. The size of the blower and thus the air pressure developed within the plenum chamber may serve to control pillowing, as may valving or gating of the air flow system entering the plenum chamber and creating the air bearing, and the stiffness or flexibility of the material used in forming the thin, flexible bottom sheet. The area of the material around the perforation pattern and between that pattern and the rigid backing member is normally the primary pillowing control means for such air pallets. The proximity of the perforation pattern to the outside edge of the plenum chamber, the slack in the plenum chamber and the rigidity of the backing member all may constitute aspects of the pillowing control.
In U.S. Pat. No. 4,272,856 directed to an air pallet-type patient mover, pillowing is controlled by having the pattern of perforations extending to the edge of the plenum chamber and the sides of the plenum chamber are purposely designed to match the head and torso of the patient from the shoulders to the hip, where the load mass of the patient is concentrated. Certain parameters with respect to the load, i.e. weight, patient size and load footprint, are matched to the plenum chamber area, otherwise the unit will not work or work poorly.
As disclosed in U.S. Pat. No. 5,561,873, it was ascertained that an air pallet plenum chamber, upon pressurization, tends to take a shape resulting in lateral reduction of the plenum chamber air-film footprint. Since the patient's body is movable and flexes, this creates significant problems. Not only is such load not rigid, but the top flexible sheet is not a rigid member. Further, only the torso and head are supported or jacked up by the plenum chamber and the rest of the body such as the legs and arms are simply carried along with the air pallet once an air bearing or air film is created by escape of air through the perforations within the thin, flexible bottom sheet to support the torso and head. Patient loading on the air pallet and removal from the air pallet also produce significant problems. Thus, the ability to create a patient mover having a size which will fit the patient, a bed, a portable gurney and a procedure table such as an operating table was recognized as being quite desirable.
These problems led initially to developments disclosed in U.S. Pat. Nos. 4,528,704 and 4,686,719. However, these developments raised other problems. The key to solving most of the problem areas seemed to lie in the utilization of a rigid backing member, but a rigid backing member made it more difficult to place the patient on the patient mover. The patient has, in such arrangements, to be physically log rolled to one side, frequently to almost a facedown position to one side so that the rigid backing member is juxtapositioned to the patient, and the patient is then rolled back over so that the patient ends up supine on the patient mover. This procedure is basically similar to placing a sheet under a patient when on a hospital bed. In such procedure, however, the sheet is usually folded in half and slid under the patient without turning his or her body excessively to one side. A rigid backing member prevented the use of such a folding procedure, however. It also restricted passage of the patient mover through passageways of restricted dimensions.
Attempts were thus made to eliminate the rigid backing member. At the same time, the separation of the jacking action from that of creation of the frictionless air film was sought. This led to the development of stacked tubes, one functioning as a pure jacking member, and the second as a combined jacking chamber and plenum chamber from which the air bearing is derived. The result was a gas pressurized jacking structure with improved load stability, in which the same compressed air pressurizing the upper chamber through a dynamic flow-through arrangement, functioned also to inflate the plenum chamber and in passing through the orifices in the thin, flexible bottom sheet, to create the air film or air bearing under the air pallet-type patient mover.
However, in such air chamber-type air patient movers, upon air pressurization of the tubular chambers formed by sealed sections of the upper two thin, flexible sheets and the air pressurization of the plenum chamber underlying all of the upper row of tubes common to the intermediate thin, flexible sheet of said row of tubes, the entire unit tended to take on a circular or cylindrical cross section. This phenomenon was termed "hot dogging". During "hot dogging," the plenum chamber tends to take on an almost circular cross section in a plane at right angles to the longitudinal axis of the series of joined tubes formed by the top thin, flexible sheet, the intermediate thin, flexible sheet and the bottom thin, flexible sheet of the air pallet. A plenum chamber is formed between the thin, flexible intermediate sheet and bottom sheet with the bottom sheet having literally thousands of closely-spaced pinholes through which air escapes from the plenum chamber to form an air film or air bearing between the thin, flexible bottom sheet and the generally rigid, planar surface beneath. Each of the transverse seal lines joining the top and intermediate sheets, which seal lines together form individual air pressurizable chambers or separate tubes, function as hinging areas allowing relative arcuate movement between adjacent tubes. The result of such hinging is a very high instability for any load in contact with the exterior of the top thin, flexible sheet forming the top of the patient mover. Furthermore, the single large sectional area formed by the plenum chamber at the bottom was not able to control the "hot dogging" and the entire air pallet patient mover was thus extremely susceptible to instability with respect to any load.
The "hot dogging" also resulted, under severe conditions, in a loss or reduction in effective air film or air-bearing, cross-sectional area which, when it becomes too small to carry the load, causes the air bearing to become inoperative. In addition, the load, or patient, might roll off the upper flexible sheet support area as the air pallet assumed a cylindrical shape and the air pallet might ground out, i.e. portions of the intermediate sheet might contact the bottom perforated sheet forcing it against the underlying supporting surface and destroying mobility, as air bearing cross-sectional area is lost. A combination of all three adverse effects might easily occur.
The phenomenon of hinging between adjacent chambers of air chamber-type air pallets using discrete separate air chambers also results in a lack of rigidity of the air chamber assembly defined by a top thin, flexible sheet and an intermediate thin, flexible sheet. As a result of separate air pressurization of each of the chambers of the upper row of tubes and the air pressurization of the lower plenum chamber, which underlies the tube array defined by the top and intermediate thin, flexible sheets, instability of the lower plenum chamber is accentuated. While the walls of the individual chambers or tubes are relatively taut, upon air pressurization, the line connections between abutting sides of the parallel row of tubes permit tube sectioning lines to act as hinges which may cause unwanted hot dogging of the air pallet as well as other overall shape instability. The presence of a load such as a patient and the weight of said patient depressing the upper surface of the air pallet tends to resist the ballooning of the air pallet and enhance the stability of the load. However, the structures inherently lack means for preventing significant lateral shrinking of the plenum chamber and other shape instabilities.
As disclosed in U.S. Pat. No. 5,561,873, an investigation of the various causes for non-rigidity in contrast to desired rigidity when attempting to substitute an air chamber or chambers for a rigid backing member led to the determination that rigidity of any part of an air chamber-type air pallet can be achieved from solely two means: (a) careful control of the air pressure within the various chambers of the air pallet, particularly with respect to control of overly high air pressure found to be undesirable due to potential ballooning, and (b) employing a solid unbendable stiff upper sheet to support the load which, for a given point or area load, spreads such load over the complete surface of the unbendable upper sheet. While the unbendable upper sheet was sufficient to provide rigidity and avoid ballooning in at least one embodiment of U.S. Pat. No. 4,528,704, the necessary rigidity can only come from the air pressure within, or, more correctly, flowing through the various chambers of the thin, flexible sheet structure.
In operation of air chamber-type air pallets of the design of U.S. Pat. No. 4,528,704, the plenum chamber being unsectionalized and linked solely to the tubular arrays at opposite ends and along opposite sides of the air pallet, such structure either creates, or enhances, non-rigidity of the structure which prevents the row of tubes of said air pallet from successfully acting as a substitute for the rigid backing member normally employed in such air pallet structures. This results in hinging between the inflated tubes, fostering ballooning of the structure, and creating instability.
In U.S. Pat. No. 5,067,189, entitled "AIR CHAMBER-TYPE PATIENT MOVER AIR PALLET WITH MULTIPLE CONTROL FEATURES", issued Nov. 26, 1991, the foregoing described problems of over pressurization causing instability of the patient mover and the load, enlargement of the underlying plenum chamber to an almost vertical circular cross section, i.e. "hot dogging", during pressurization, the requirement for a rigid or semirigid backing member to prevent "hinging" between individual longitudinal chambers or tubes for supporting the load, and the point load grounding out on the underlying support surface due to load shifting were tentatively resolved. During the course of improving the earlier air pallet patient movers of the air chamber type, it was found that all of the recited problems with prior types of inflatable air pallets were substantially interrelated, as well as the discovery of an additional structural problem described as the reduction or shrinkage of the lateral dimension of the air pallet. U.S. Pat. No. 5,067,189 reduces the recited problems through a novel interrelated structure. In lieu of a rigid or semirigid backing member, a series of stacked rows of pressurized chambers or tubes are utilized to create a predetermined air dispersion which, in concert with the air dispersion in the underlying plenum chamber, properly jacked the load, e.g. a patient, and maintains the flexible backing surface (the stacked rows of tubes or chambers) in a planar direction generally parallel to the underlying developed air film. Simultaneously, the plenum chamber is inflated and through the underlying perforations, creates an air film between the air pallet and the fixed support surface, but only in an area which generally matches the footprint of the load. Further, the inflation of the plenum chamber within the parameters set forth in U.S. Pat. No. 5,067,189 creates a sufficient pillowing means to permit the air pallet to accommodate surface irregularities and move the load on the developed air film without bottoming out and without the bottom flexible sheet ballooning outward. This is accomplished through a series of vertical and oblique ties which restrain the separation of an intermediate sheet forming the bottom of the linked rows of chambers or tubes and the underlying bottom sheet of the plenum chamber from moving outward one from the other beyond a predetermined distance or dimensions. These ties (or stringers) in combination with the stacked rows of chambers or tubes, prevent "hot dogging" of the air pallet when inflated, tends to reduce lateral shrinkage of the air pallet because of its "anti-hot dogging" and anti-ballooning effect, and increase the ability of the air pallet to accommodate surface irregularities when in motion so as not to create a point load problem, all of which increase the load stability of the particular air pallet.
The invention disclosed in U.S. Pat. No. 5,561,873 entitled "AIR CHAMBER-TYPE PATIENT AIR PALLET WITH MULTIPLE CONTROL FEATURES" improves upon the inventions of the U.S. Pat. No. 5,067,189 patent by providing between a top sheet and bottom or intermediate sheet, a more or less rectangular array of centrally positioned chambers laterally oriented and separated from each other by a series of substantially vertical walls comprised of lateral and longitudinal partition members or walls secured to the top and bottom sheets, or in some embodiments where a separate bottom planar chamber, or plenum chamber, is used, an intermediate sheet. The lateral and longitudinal partition members are secured to the top and bottom or intermediate sheets by sewing, thermal welding or the like and essentially serve to prevent the top sheet and underlying sheets from expanding too far from each other, which effectively prevents "ballooning" and so-called "hot dogging" yet allows effective "jacking" and "pillowing" at the same time achieving effective stability and preventing both lateral and longitudinal shrinkage. Essentially free passage of pressurized air is allowed between the various laterally-oriented central chambers and a peripheral chamber extending completely around the rectangular array of central chambers. As disclosed in the patent, the combination of the central array of lateral chambers and securing of the lateral and longitudinal partition members to the top and bottom or intermediate sheets in the center, prevents ballooning and hot dogging, together with the lateral and longitudinal shortening occasioned by ballooning as the result of the vertical expansion occasioned by ballooning. Also, because of the way the lateral and longitudinal partition members are combined, a very strong tacked or secured structure which has little tendency to stress tearing of the sewing or heat welding lines, is provided. Two types of lateral and longitudinal partition members are disclosed, one of which makes use of separate members with the longitudinal members disposed at the ends of the transverse chambers formed by the lateral partition members and the other in which the longitudinal partition members are discontinuous as the result of being formed by a right-angled turn of the lateral partition members plus an opening at the end to allow free circulation of gas or low cubic foot per minute air throughout the structure.
When the longitudinal partition members are not discontinuous, they have orifices provided in them and are preferably tacked to the top and bottom or intermediate sheets slightly beyond the ends of the lateral partition members to allow free circulation of pressurized air between the various lateral chambers of the rectangular array of chambers as well as with the outer peripheral rectangular chamber. The lateral partition members may be secured within the rectangular array of chambers in an inclined orientation to facilitate lying down of such partition members uniformly in a deflated position.
While the invention of the U.S. Pat. No. 5,561,873 patent has been quite successful and has solved major problems previously existing in medical patient transfer devices and the like, there is room for improvement, some of which improvements are provided by the present invention.
Perforated upper sheets have also been used in hospital environments to provide so-called "low air loss" type arrangements in which low pressure air is blown upwardly against a patient reclining upon the apparatus, not to lift the patient, but to essentially prevent the skin of the patient from becoming too moist and breaking down into bed sores and the like. This type of air loss apparatus is also used in connection with burn patients.